import java.util.*;

public class Solution15 {
    public static void main(String[] args) {
        List<List<Integer>> a = threeSum(new int[]{-1, 0, 1, 2, -1, -4});
        System.out.println(a);
    }

    public static List<List<Integer>> threeSum(int[] nums) {
        List<List<Integer>> ans = new ArrayList<>();
        int len = nums.length;
        if (len < 3) return ans;
        Arrays.sort(nums);
        for (int i = 0; i < len; i++) {
            if (nums[i] > 0) {
                break;
            }
            if (i > 0 && nums[i] == nums[i - 1]) {
                continue;
            }
            int l = i + 1;
            int r = len - 1;
            while (l < r) {
                int sum = nums[i] + nums[l] + nums[r];
                if (sum == 0) {
                    ans.add(Arrays.asList(nums[i], nums[l], nums[r]));
                    while (l < r && nums[l] == nums[l + 1]) l++;
                    while (l < r && nums[r] == nums[r - 1]) r--;
                    l++;
                    r--;
                } else if (sum < 0) l++;
                else r--;
            }
        }
        return ans;
    }
}
